Numerous experimental approaches have provided information about the subcellular distribution of phytochromes. With rare exception the assays depend ultimately upon either spectrophotornetric or immunochernical detection to verify the presence of a phytochrome species within a particular cellular compartment. The interpretation of these results is ambiguous at best. We propose to investigate the localization of various phytochromes through the fluorescence emission generated by excitation of a phytochrome-green-fluorescent protein fusion protein. It is our hope that multi-photon microscopy will allow for a real time analysis of phytochrome localization which can be correlated with the physiological role for thit protein.